The answer unfortunately is you should save the smallest size you will use, and only you know that. We save anything at least 1.5" x 2.5", but we have a plan for that size scrap (pineapple quilt). You may think that is a useless size and would toss it. Others may go even smaller (the traditional size for postage stamp quilts is 1" - which is .5" finished). It really is personal.